There is already known a device for tempering a musical signal with an ensemble effect, wherein the musical tone signal input is mixed with a further musical signal, the frequency of which is continuously varied upwards and downwards from the frequency of the original musical tone signal, said further musical signal being produced by modulating the delay time of the original musical tone signal by means of a plurality of sinusoidal wave modulating signals, the phases of which differ by a uniform angle. Alternatively, the modulating signals can be such as to produce a double modulation with a frequency as low as about 1/10 of that of the modulating signal. The modulating period corresponds to a low frequency of 0.2-1 c/s. However, because each of the modulated musical tone signals is a signal having a slight vibrato and the phase differences between modulation signals are uniform, the vibrato effects will cancel each other and will make the ensemble effect audible. However, the vibrato effect is not completely eliminated so that an adequate ensemble effect has not yet been achieved.